Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned partially or fully behind the panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. Touch screens can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object at a location often dictated by a user interface (UI) being displayed by the display device. In general, touch screens can recognize a touch and the position of the touch on the touch sensor panel, and the computing system can then interpret the touch in accordance with the display appearing at the time of the touch, and thereafter can perform one or more actions based on the touch. In the case of some touch sensing systems, a physical touch on the display is not needed to detect a touch. For example, in some capacitive-type touch sensing systems, fringing electrical fields used to detect touch can extend beyond the surface of the display, and objects approaching near the surface may be detected near the surface without actually touching the surface.
In addition to touch panels/touch screens, many electronic devices may also have mechanical inputs (or mechanical input mechanisms), such as buttons, switches, and/or knobs. These mechanical inputs can control power (i.e., on/off) and volume for the electronic devices, among other functions. However, interfacing mechanical inputs, particularly rotational mechanical inputs, to an electronic device may require electronic instrumentation which may be difficult to integrate into the electronic device, for example because the instrumentation may be undesirably large, may require high power consumption, or may require complex processing, or may be subject to environmental interference. Further, conventional technologies for providing rotational mechanical input can exhibit limited dynamic range and non-linear response, both of which can complicate integration of the mechanical input into larger systems.